Chair backrest



FIG. 1 is a perspective view of a chair backrest showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is another perspective view thereof.

The broken line showing of the chair backrest is for the purpose of illustrating portions of the article and forms no part of the claimed design. 

CLAIM The ornamental design for a chair backrest, as shown and described. 